1. Field of the Invention
The present invention relates to a programmable timer unit for use in a remote control load management system, such as for controlling the illumination loads according to a user's defined pattern or schedule.
2. Description of the Prior Art
A remote control load management system is widely utilized in the art for controlling the illumination loads. One such typical prior art system is shown in Japanese Patent Publication No. 2-144604, which is arranged to control the illumination loads connected to a common transmission line, and includes a programmable timer unit in order to turn on and off the illumination loads according to the user's defined schedule. The system basically includes a central controller, a switch terminal, and a load terminal that are connected with each other over the transmission line for a time-division multiplexing signal intercommunication therebetween. The switch terminal is equipped with one or more switches each of which is manipulated by a user for turning on and off one or more associated illumination loads, and with an intelligent module which is responsible for communicating with the central controller to send a command of actuating the illumination load or loads under the control of the central controller. The load terminal is connected to one or more loads and is also equipped with an intelligent module responsible for communicating with the central controller to receive the command of actuating the loads. For this purpose, the switch terminal is given a particular switch address allocated to the switch as well as a particular control code assigning an intended method for actuating the associated load or loads. The load terminal is also given a particular load address allocated to each load connected to the load terminal. The central controller stores an address table relating each of the switch addresses to one or more load addresses, as well as a control table relating each of the control codes to the control method for actuating the load or loads. In operation, as the switch is manipulated, the intelligent module of the switch terminal generates an event signal and transmit it to the central controller together with the switch address and the control code assigned to the switch. In response to the event signal, the central controller references the address table and the control table to obtain a destined load address and an intended control method, and provides a control signal indicative thereof to the load terminal, which responds to actuate the corresponding load in a manner as designated by the control method. The programmable timer unit included in the system has an input section for selecting a schedule specifying the target load, an actuation time for operating the load, as well as the control code for the load. Thus specified schedule is written into a load management program which is executed to give a timer signal to a dedicated intelligent terminal which in turn translates it into the command analogous to that issued from the switch terminal. Then, the command is sent from the dedicated intelligent terminal to the central controller in order to actuate the target load according to the schedule written in the load management program. The dedicated intelligent terminal is designed to have its own switch address which is analogous to that of the switch terminal and is set in most cases to be identical to the switch address in order to make the combination of the programmable timer unit and the dedicated intelligent terminal as an alternative of the switch. As the timer signal from the programmable timer unit is simply an ON/OFF signal as is generated by the switch in the switch terminal, the intelligent terminal has to be combined for generating the command to be capable of being interpreted at the central controller for actuating the target load.
However, since the dedicated intelligent terminal is allowed to have only a limited number of switch addresses, one or more additional intelligent terminals have to be connected to the programmable timer unit as the programmable timer unit is required to function as alternatives of more number of the switches for controlling a large number of the loads. This poses a problem of requiring an enlarged mounting space and an increased cost for satisfying more sophisticated load management.